Night Caching is one aspect of the hobby that many people find enjoyable. Night caching can be as simple as finding regular caches at nighttime under cover of darkness (the difficulty and terrain ratings can go way up at night) or by hunting specially designed caches that can be found more easily (or found only) at night.
For hunting regular caches at night, you'll want to bring all your usual caching equipment plus a big flashlight and a white LED headlamp. Get the biggest, brightest flashlight you can afford. Get the brightest LED headlamp you can, and make sure it's a comfortable one.
For hunting night-only caches, many players find that it is best to leave the really big bright flashlight off and just navigate using a moderately bright LED headlamp. Why? Most night-only caches are deployed using small reflectors tacked onto trees and other objects. These can't be seen easily by day, but at night they jump righto out at you. The problem with using a big bright flashlight is that it lights up the trees and other objects too, making it harder to see the reflector. By contrast, the faint light from a white LED headlamp doesn't illuminate the brush as much, and the reflectors just pop out at you, helping you navigate.
Night caching can be fun, but be aware that wild animals and criminals come out at night. Be prepared. Know your area. Don't go alone. Carry some form of legal self-protection and know how to use it. Carry a cellphone. Let someone know where you are going and when you might expect to be back.
Most of all, have fun. Caching's cooler at night.